Nitrogen-Doped Graphene with a Three-Dimensional Architecture Assisted by Carbon Nitride Tetrapods as an Efficient Metal-Free Electrocatalyst for Hydrogen Evolution

Abstract

Current polymer membrane‐based electrolyzers use Pt as a cathode catalyst for efficient reduction of water. The high cost of Pt‐based catalysts forces researchers to develop alternative electrocatalysts. Here, a simple strategy has been proposed to synthesize a metal‐free electrocatalyst for the hydrogen evolution reaction (HER) by high‐temperature annealing of graphene oxide‐coated melamine foam. The prepared catalyst possesses both structural and functional advantages with its three‐dimensional (3D) interconnected arms of carbon nitride (CNx) backbone wrapped with nitrogen‐doped graphene (N‐RGO) sheets (CNx@N‐RGO). CNx@N‐RGO faces only a 193 mV overpotential to achieve a current density of 10 mA cm−2, which is far superior to the previously reported Pt‐free systems. Along with the high exchange current density 34.7×10−6 A cm−2 and low Tafel slope of 54 mV dec−1, CNx@N‐RGO follows a Volmer‐Heyrovsky mechanism for the HER. DFT calculations show that the synergy between CNx and N‐RGO facilitates good electrical coupling between the two moieties and provides optimal binding to H+ ions on the catalyst that, in turn, results in efficient reduction of hydrogen ions.